Transport properties of ZIF-8 nanocrystals for hydrogen adsorption: Molecular dynamics study

HS He and DL Feng and XX Zhang and YH Feng, JOURNAL OF ENERGY STORAGE, 72, 108270 (2023).

DOI: 10.1016/j.est.2023.108270

Intracrystalline and intergranular heat and mass transport properties make a significant difference to microcrystalline metal-organic frameworks (MOFs) nanoparticles for hydrogen energy storage applications. Here, we perform molecular dynamics (MD) to investigate the nanoscale mechanism of the thermal conductivity changes of zeolite imidazolate frameworks-8 (ZIF-8) due to the adsorption and diffusion of H2. Self-diffusivity and vibration state of density analysis verifies that the H2 adsorbates as energy carriers in ZIF-8 cages can provide heat pathways to enhance the overall thermal transport performance, although additional phonon scattering is introduced. Further, we explore the interfacial thermal resistance and hydrogen permeability of the ZIF-8 armchair-type hydrogen-termination surface. The thermal resistance of the coherent interface of ZIF-8 is predicted to be 42.3 m2 K-1 GW-1. We also simulate the dynamic process of hydrogen adsorption into ZIF-8 slabs to study the interfacial molecule transport properties. By comparing the equivalent lengths of interfacial heat and mass transfer, we find that the kinetics performance of ZIF-8 is more easily to be limited by the large thermal resistance at the coherent interface of nanocrystals.

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